<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>for-in 循环</title>
</head>
<body>
<script>
    var value;
    for(value in document){
        println(value);
    }

    function println(a){
        document.write(a);
        document.write('<br/>');
    }

</script>
</body>
</html>